add scale factor to set viewport for retina screenshots (#691)

* device scale

* fix node.js daemon

* fix cargo fmt formatting for scale factor code

* fixes

src/protocol.ts

@@ -270,6 +270,7 @@ const viewportSchema = baseCommandSchema.extend({
   action: z.literal('viewport'),
   width: z.number().positive(),
   height: z.number().positive(),
+  deviceScaleFactor: z.number().positive().optional(),
 });
 
 const userAgentSchema = baseCommandSchema.extend({